Calculate the answer. express it in scientific notation and include the correct number of significant figures.
(12 x 10^4) x (5 x 10^-2)
6 x 10^3
6.0 x 10^2
6 x 10^6

6x10^3

Explanation:

By multiplying (12 x 10^4) and (5 x 10^-2) we get

120000 x 0.05 = 6000

Since we are multiplying, the number of significant figures we need comes from the number with the least amount of sig figs in the problem (5 x 10^-2 has only 1 sig fig, 12 x 10^4 has 2). Therefore, our answer should only have 1 significant figure and we get 6 x 10^3.

first, consult an activity series chart to determine if al is more reactive than fe. it is, so it will replace the fe. now, one can continue with the problem.

next, make sure you have a correctly balanced equation.

3feo + 2al ==> 3fe + al2o3

now, determine which reactant (feo or al) is in limiting supply.

moles feo present = 125 g x 1 mole/71.8 g = 1.74 moles

moles al present = 25.0 g x 1 mole/26.98 g = 0.927 moles

since from the balanced equation, it take 3 mol feo for every 2 mol al, al will be limiting.

you can determine this simply by dividing moles of each by their coefficient in the balanced equation. for example: 1.74/3 = 0.58 and 0.927/2 = 0.464. al is less, so it is limiting.

finally, using the stoichiometry in the balanced eq. determine mass of fe that can be produced from 0.927 moles of al.

0.927 moles al x 3 moles fe/2 moles al x 55.8 g/mole = 77.6 g